500 (internal server error) at laravel ajax

I have set the meta and header for ajax setup and already done a action with ajax.
But this time at same place I have faced the error.
I can't find out my problem.

var per = new Array();
             $("input[name='permission']:checked").each(function() {
               per.push($(this).val());
             });
             $.ajax({
               url:"/admin-role",
               method:"POST",
               data:{
                 "_token": "{{ csrf_token() }}",
                 "role_name":role_name,
                 "permission":per

               },
               dataType:'json',
               success:function(response){
                   console.log(response);
               }
               // success:function(response){

               //   if (response.status=='errors') {
               //     Swal.fire(
               //           response.message
               //         )
               //   }
               //   if (response.status=='success') {
               //       Swal.fire(
               //           response.message
               //         )
               //       $('#roleModal').modal('hide');
               //       $("#role_create_form")[0].reset();
               //       $('.table').load(location.href + ' .table');
               //     }
               // }
             });